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MULTIRESIDUE PESTICIDE ANALYSIS IN FRUIT AND VEGETABLE COMMODITIES USING BOTH UPLC AND APGC ON A SINGLE MASS SPECTROMETER PLATFORM Kari Organtini

1, Simon Hird

2, Eimear McCall

2, and Gareth Cleland

1

1 Waters Corporation, 34 Maple St, Milford, MA 01757

2Waters Corporation, Stamford Avenue, Altrincham Road, SK9 4AX Wilmslow UK

INTRODUCTION Hundreds of pesticides are commercially available and approved

for use on various crops making pesticide residue analysis an

important component of ensuring food safety. Maximum Residue

Levels (MRLs) are set at the highest level of pesticide that would

be expected to be found in that crop when it has been treated in

line with good agricultural practice. National authorities control

and enforce MRLs by testing samples for pesticide residue levels

using analytical surveillance programs. These programs check for

compliance with MRLs, assess dietary exposure, and check for use

of unauthorized pesticides. The food industry also carries out its

own due diligence analyses. With the large amount of pesticides

available for use, it is important to be able to rapidly and reliably

analyze samples for many pesticides in a single method. Mass

spectrometry coupled with both gas (GC) and liquid

chromatography (LC) is needed to provide comprehensive analysis

of a wide range of pesticide residues with sufficient sensitivity to

meet global MRL regulations. The use of Quick, Easy, Cheap,

Efficient, Rugged and Safe (QuEChERS) sample extraction and

clean up has streamlined analytical efficiencies for multi residue

analyses.1 The advantage of ultra performance liquid

chromatography (UPLC) coupled with tandem quadrupole mass

spectrometry (MS/MS) for multi residue pesticide analysis is widely

reported.2 More recently the use of GC-MS/MS operated at

atmospheric pressure (APGC) has been shown to offer significant

improvements in performance over electron impact (EI) for

challenging pesticides, in terms of selectivity, specificity and

speed of analysis.3, 4

For this analysis, a single workflow for multi

residue analysis of pesticides is demonstrated on a variety of fruit

and vegetable samples on the same tandem quadrupole MS

instrument, with less than 30 minutes needed to switch between

chromatographic inlets. The performance of the method is

highlighted in terms of sensitivity, repeatability, and linearity for

both LC and GC in compliance with the SANTE guidelines

(11945/2015) for pesticide analysis.5

CONCLUSIONS Complex multi residue pesticide analysis was demonstrated

using both UPLC and APGC analysis on the same tandem

quadrupole instrument

Instrument methods were generated and maintained using QuanPedia databases making method generation and

maintenance fast and simple.

The reliable scanning speed of the TQ-S micro produced accurate and precise measurements for large multi residue

methods.

The performance of the analysis complied with the SANTE

guidelines for pesticide residue analysis.

Detection at the default maximum residue limit of 0.010 mg/kg was easily achieved for > 99% of pesticides analyzed with good

precision (RSDs < 10%) for most analytes in the food samples.

The flexibility of the Universal Source architecture provides access to both UPLC-MS/MS and GC-MS/MS on the same instrument, allowing for an increase of laboratory efficiency,

while maintaining required sensitivity and repeatedly.

References

1. D. Shah, E. McCall, G. Cleland. Single LC-MS/MS Method for Confirmation and Quantification of Over 400 Pesticides in a Complex Matrix Without Compromising Data Quality. Waters Application Note 720005559EN. January 2016.

2. Kovalczuk T., Jech M., Poustka J., Hajslova J., 2006, UPLC-MS/MS: A novel challenge in multiresidue pesticide analysis in food, Analytica Chimica Acta, 577.

3. Tienstra M., Portoles T., Hernandez F., Mol J.G.J., 2015, Fast gas chromatographic residue analysis in animal feed using split injection and atmospheric pressure chemical ionisation tandem mass spectrometry, J. Chrom. A., 1422.

4. Cherta L., Portoles T., Beltran J., Pitarch E., Mol J.G.J., Hernandez F., 2013, Application of gas chromatography- mass spectrometry with atmospheric pressure chemical ionisation for the determination of multiclass pesticides in fruits and vegetables, 1314.

5. European Commission. SANTE/11945/2015. Guidance document on analytical quality control and method validation procedures for pesticides residues analysis in food and feed. 2015, rev. 0.

RESULTS AND DISCUSSION

Figure 2. The fast scanning of the Xevo TQ-S micro collects the re-quired data points (minimum 12 points per peak) while maintaining peak quality.

Figure 3. Matrix matched calibration curves and chromatograms for standards at 0.001 mg/kg. (A) APGC analysis of leptophos in celery and lemon, (B) UPLC analysis of carbofuran in corn and kale.

Figure 4. Percentage of pesticides detected in the 0.010 mg/kg standard for each matrix using both APGC and UPLC.

Figure 5. Percentage of compounds detected at 0.010 mg/kg at respec-tive RSDs.

Figure 1. Xevo TQ-S micro with the Universal Source allowing for UPLC and APGC analysis on the same mass spectrometer.

Fast Scanning Speeds of Xevo TQ-S micro

Each analysis method contained approximately 200 pesticide residues acquiring at least 2 MRM transitions per compound. The mass spec-trometer must be able to rapidly scan through all of the MRM channels to acquire the required data (Figure 2).

Pesticides in Matrix

Matrix matched standards were prepared in matrix over a range of 0.001 - 0.050 mg/kg. Replicate injections made using the UPLC and APGC methods. In accordance with the SANTE/11945/2015 guidelines,

the data

were fitted with the best fit calibration; for the UPLC data, the response was shown to be linear whereas the APGC response was best fitted with a quadratic calibration.

5 (Figure 3). A majority of the compounds in both

analysis methods had correlation coefficient (R2) values of 0.995 or

greater with residuals from triplicate injections within ±20%.

METHODS Sample Extraction and Cleanup

APGC-MS/MS Parameters

GC System: 7890A

Autosampler: CTC PAL RTC

Column: 30 m x 0.25 mm x 0.25 µm Rxi-5MS

MS System: Xevo TQ-S micro

Ionization mode: API+

Ionization mechanism: Proton transfer (3 vials of water in source)

Commodities Studied

Four different classes of food commodities were studied:

Pesticide Residue Classes

Each analysis method (APGC and UPLC) contained approximately 200 pesticide residues from various classes.

UPLC pesticide classes: APGC pesticide classes:

Method Generation and Management using QuanPedia

MS Methods, TargetLynx Processing Methods, and UPLC Methods were generated and maintained using QuanPedia databases.

For full method details, see Waters application note 720006013en

UPLC-MS/MS Parameters

LC System: ACQUITY UPLC H Class

Column: ACQUITY BEH C18 2.1 x 100 mm, 1.7um

Mobile Phase A: Water + 10 mM ammonium acetate

Mobile Phase B: Methanol + 10 mM ammonium acetate

MS System: Xevo TQ-S micro

Ionization Mode: ESI+

Organophosphorus

Carbamates

Organonitrogen

Organophosphorus

Organochlorine

Organonitrogen

Pyrethroids

Herbicide Methyl Esters Sample MgSO4 PSA GCB Volume

Celery 150 mg 25 mg 7.5 mg 1 mL Lemon 150 mg 25 mg - 1 mL Corn 150 mg 25 mg - 1 mL Kale 900 mg 150 mg 150 mg 6 mL

Table 1. dSPE cleanup conditions used for each sample matrix.

Figure 4 demonstrates the percentage of pesticides in each method de-tected in the spiked matrices at 0.010 mg/kg, but many pesticides could also be detected at 0.001 mg/kg. The precision of the measurements was excellent with > 90% of the detected pesticides exhibiting RSDs less than 10% (n=3), except the APGC kale analysis which had > 80% of pesti-cides exhibiting RSDs less than 10% (Figure 5). Ion ratios in matrix were also shown to be within 30% tolerance of the reference values.